The oldest denomination in the state is the Roman Catholic Church, and it remains the largest today. Spanish efforts to plant missions in Pimeria Alta (Arizona) were abortive well into the 1800s. The Jesuits fell out of favor and were followed by the Franciscans, who fared no better. In 1833 the missions yielded to the Mexican Act of Secularization and succumbed to decay. Only a tiny fraction of vital and historical records are extant. In modern times, the state is served by two dioceses. The Diocese of Phoenix is located at 400 E. Monroe St., Phoenix, AZ 85004-2336; and the Diocese of Tucson: 111 S. Church Ave., P.O. Box 31, Tucson, AZ 85702-0031, Archives: 880 E. 22nd St., Tucson, AZ 85710. The websites for both dioceses have links to individual parishes.

The second largest denomination in the state is The Church of Jesus Christ of Latter-day Saints, or Mormons, who came to the state originally as missionaries from Utah to the Native Americans. However, permanent Mormon colonies were not established until 1877, when settlers arrived and founded towns throughout the state with a major center growing up in Mesa (a modern suburb of Phoenix). These colonies provided the bases from which a predominant Mormon population in parts of the state developed and remain today. All congregation records, mission reports, and genealogical sketches for church members are on microfilm at the FHL. The Church also operates the huge Mesa Family History Center, which has its own building adjoining the Mesa temple grounds and is open to the public. This has developed into a major genealogical library in the state.

The Episcopal Church in the state is served through the Episcopal Diocese of Arizona, 114 W. Roosevelt St., Phoenix, AZ 85003-1406. The Episcopal presence in the state dates from 1865 when Arizona and Nevada were constructed as a missionary jurisdiction. In 1874 Arizona was separated out. The diocese website has contact information and links to parishes throughout the state.

The United Methodist Church is served through the Desert Southwest District, 1550 E. Meadow Brook Ave., Ste. 200, Phoenix, AZ 85014-4040. This district office should be contacted as a starting place for Methodist records.

The Jewish presence in the state has also been strong. The Arizona Jewish Historical Society, 4710 N. Sixteenth St., Ste. 201, Phoenix, AZ 85066 seeks to record the Jewish contribution to the state in areas of politics, economics, social, and cultural history. There are also several major collections that should be considered in Jewish research. The Leona G. and David A. Bloom Southwest Jewish Archives at the University of Arizona Library in Tucson holds a wealth of information on the Jewish experience in West Texas, New Mexico, Arizona, and Southern California. The University of Arizona Library also holds the Rochlia Collection of Arizona Jewish History, which has oral interviews and historical material. Arizona State University holds the Shema Arizona: The Arizona Jewish Historical Society Oral History Project.